The overall purpose of this Phase I SBIR application is conduct of research to address the scientific and technical feasibility of using diammine (also spelled diamine in the literature) silver fluoride as a topical agent to arrest the progression of tooth decay, and to conduct the initial work that, in the longer run, will result in FDA 510 K approval of an indication for diammine silver fluoride as a tooth decay arresting agent. The research will be conducted by a collaboration of the small business firm ADP Silver Dental Arrest, LLC, and experienced researchers at the University of Connecticut School of Dental Medicine. The Specific Aims are to: 1) Use a human caries model experiment in well-characterized rats to determine whether a single brief topical diammine silver fluoride treatment can inhibit the progression of already-established extensive carious lesions and 2) Conduct a single dose topical administration study to assess potential toxicity of diammine silver fluoride. Alarming new national epidemiologic data documents the increase in tooth decay in preschool children (Dye et al., 2007) at the same that there are serious inequities in access to care for the poor and for minorities. The same problem exists for the elderly and institutionalized where inexpensive solutions to arresting root caries are badly needed. Given increased disease impact in some parts of the population coupled with poor access, it is likely that the disparities will increase. New technology is not being developed and brought to the marketplace fast enough to address the problem. Public Health Significance: The overall purpose of this Phase I SBIR application is conduct of research to address the scientific and technical feasibility of using diammine (also spelled diamine in the literature) silver fluoride as a topical agent to arrest the progression of tooth decay, and to conduct the initial work that, in the longer run, will result in FDA 510 K approval of an indication for diammine silver fluoride as a tooth decay arresting agent. [unreadable] [unreadable] [unreadable]